Tools with respect to workpieces in environmental chambers

ABSTRACT

ONE WALL OF AN ENCLOSURE UNIT THAT BOUNDS A WORKING CHAMBER IS FORMED WITH A FIRST APERTURE WHICH IS SEALED OVER BY A FIRST COVER PLATE ROTATABLE ABOUT A CENTRAL AXIS OF THE APERTURE. THE FIRST COVER PLATE HAS AN ECCENTRIC SECOND APERTURE WHICH IS SEALED OVER BY A SECOND COVER PLATE ROTATABLE ABOUT A CENTRAL AXIS OF THE SECOND APERTURE, THE SECOND COVER PLATE BEING APERTURED ECCENTRICALLY TO PERMIT THE SEALED PASSES THERETHROUGH OF MEANS FOR OPERATING UPON A STATIONA-   RY WORKPIECE IN THE CHAMBER. COMBINED ROTATIONS OF THE TWO COVER PLATES CAN PRODUCE MOVEMENT OF THE POINT OF OPERATION OVER THE WORKPIECE IN VARIOUS DIRECTIONS PARALLEL TO THE SAID ONE WALL.

O -28-71 OR, 3.588.442

uuluiu claws Patent [72] inventor Kenneth Walter O'Riley Surrey, England [21] Appl. No. 817,061

22 Filed Apr. 17, 1969 [45] Patented June 28, 1971 [73] Assignee Viclrers Limited London, England [32] Priority Apr. 26, 1968 [33] Great Britain [3 l 1 20,034/68 [54] TOOLS WITH RESPECT TO WORKPIECES IN Primary Examiner.l. V. Truhe Assislant Examiner- Robert O'Neill Attorney-Pennie, Edmonds, Morton, Taylor and Adams ABSTRACT: One wall of an enclosure unit that bounds a working chamber is formed with a first aperture which is sealed over by a first cover plate rotatable about a central axis of the aperture. The first cover plate has an eccentric second aperture which is sealed over by a second cover plate rotatable about a central axis of the second aperture, the second cover plate being apertured eccentrically to permit the sealed passage therethrough of means for operating upon a stationary workpiece in the chamber. Combined rotations of the two cover plates can produce movement of the point of operation over the workpiece in various directions parallel to the said one wall.

PATENTED M28197! i V m m h F V TOOLS WITH RESPECT TO WORKPIECES IN ENVIRONMENTAL CHAMBERS This invention relates to the movement of tools with respect to workpieces in environmental chambers, for example when it is necessary to operate with a moving too] upon such a workpiece maintained under a selected chamber pressure which is higher or lower than the atmospheric pressure outside the enclosure bounding and defining the environmental chamber.

For example, enclosure units are required to provide vacuum chambers for enabling electron-beam welding processes to be carried out under greatly reduced pressures. Such a process is generally carried out with the electron beam and the workpiece in a vacuum, for example at a pressure of mm.Hg. in a vacuum chamber bounded by metal walls. Commonly the electron gun producing the electron beam is mounted to deliver its beam into the vacuum chamber via a fixed aperture in one of the walls bounding the chamber. Such fixing of the point of entry of the electron beam into the vacuum chamber, through the apertured wall bounding the chamber, obviates any need for a movable seal between the wall and the electron gun. A movable table within the vacuum chamber carries the workpiece and moves it as desired with respect to the electron welding beam. It is usual to provide drive means for moving the work table selectively in two mutually perpendicular directions, known respectively as the x and y directions. In order to avoid any need to provide movable vacuum seals around driving mechanisms passing through the walls bounding the chamber, it is common to have such driving mechanisms, insofar as driving in at least one of the x and y directions is concerned, located wholly within the vacuum chamber. Unfortunately, such driving mechanisms tend to wear rapidly in the chamber, since lubricants evaporate rapidly in the vacuum conditions employed there.

An alternative is to remove the need to provide say ydirection driving means within the chamber, by enabling the point of entry of the electron beam into the chamber to be moved in the y-direction. Thus the aperture for passing the beam into the chamber may take the form of a slot, which extends perpendicularly to two opposite sides of the chamber and is sealed over by means of a strip-form rigid cover plate which can slide over the slot in its longitudinal direction (the y-direction) whilst supporting the electron gun over a fixed aperture in the cover plate. A flexible sealing strip extends completely around the slot and cooperates with the cover plate sliding thereon to maintain a gastight seal. However, if the length of the slot is greater than half the distance between the aforesaid two opposite sides of the chamber, when the electron gun is at one or other end of the slot the sliding cover plate will project substantially beyond the adjacent oneof the said two opposite sides. Such projection is inconvenient, to an extent which is unacceptable in many engineering situations and additional means are still required for bringing about movement of the workpiece, with respect to the electron beam, in the x-direction.

An embodiment of the present invention employs an enclosure unit, for separating a workpiece from the ambient atmosphere, comprising wall means bounding a chamber for accommodating the workpiece, the wall means having edge regions which define a first aperture in the wall means, and further comprising a first cover which has peripheral regions extending along the said edge regions and is rotatable with respect to the wall means about a first axis passing centrally and perpendicularly through the first aperture and has inner edge regions which define a second aperture located eccentrically with respect to the first aperture, a second cover which has peripheral regions extending along the inner edge regions of the first cover and is rotatable with respect to the first cover about a second axis passing centrally and perpendicularly through the second aperture and has inner edge regions defining a third aperture which is located eccentrically with respect to the second aperture, first slidable seal means extending completely around the first aperture between the said wall means and the first cover to maintain a substantially vacuumtight seal therebetween during rotation of the first cover,

second slidable seal means extending completely around the second aperture between the first and second covers to maintain a substantially gastight seal therebetween duririg rotation of the second cover, and a sealing device mounted on the second cover and extending completely around the third aperture for cooperating with a tool to form a substantially vacuum-tight seal over the third aperture, whereby a stationary workpiece located in the chamber when the unit is in use can be operated upon by means of the tool at a point which can be moved over the workpiece by rotation of the two covers.

In the present invention, for enabling an electron-beam welding process to be carried out, the said tool is an electron gun, and the outlet end of the electron gun is connected with the said second cover by means of the said sealing device which is designed to provide a vacuum-tight seal around the said third aperture. in such an embodiment there is no need to provide x or y direction driving mechanism within the chamber, since movement in both the x and y directions is possible by a combination of rotations of the first and second covers.

Preferably the said first aperture is circular and the said peripheral regions of the first cover define a circular edge thereof that fits freely within the said edge regions defining the first aperture. In such a case the first cover may have a major portion forming a spigot, bounded laterally by the said circular edge, for locating the first cover with respect to the first aperture, and may have at one end of the spigot portion a flange portion projecting radially outwardly beyond the said edge regions defining the first aperture. A thrust race may then be mounted between the flange portion and the said wall means so as to surround the first aperture and facilitate rotation of the first cover with respect to the wall means. The said first slidable seal means may be located within the first aperture, so as to provide a substantially vacuum-tight seal between the said circular edge and the said edge regions defining the first aperture.

Preferably the said second aperture is circular and the said peripheral regions of the second cover define a circular edge thereof that fits freely within the said inner edge regions defining the second aperture. In such a case the second cover may have a major portion formed as a spigot, bounded laterally by the said circular edge of the cover, for locating the second cover with respect to the second aperture, and may have at one end of its spigot portion a flange portion projecting radially outwardly beyond the said inner edge regions defining the second aperture. A thrust race may then be mounted between the first cover and the flange portion of the second cover, surrounding the second aperture so as to facilitate rotation of the second cover with respect to the first cover plate. The said second slidable seal means may be located within the second aperture, so as to provide a substantially vacuum-tight seal between the said circular edge of the second cover and the said inner edge regions defining the second aperture.

It may prove desirable to market a unit embodying the invention, for use in carrying out electron-beam welding processes, wherein the sealing device is constructed tin-provide a slidable seal which permits the electron gun to be rotated during use, with respect to the second cover, about an axis passing perpendicularly through the third aperture.

Preferably the said first axis and a third axis, which passes centrally and perpendicularly through the third aperture, parallel to the first and second axes, are equidistant from the said second axis.

Reference will now be made, by way of example, to the accompanying drawing, in which:

FIG. 1 is a diagrammatic plan view of a vacuum chamber enclosure unit embodying the present invention, and

H6. 2 is a sectional view of an upper part of the unit when in use, the sectional plane corresponding to the line 11-11 of FIG. 1.

A vacuum chamber for accommodating the workpiece, whilst being welded by means of an electron beam, is provided in a boxlike structure 1 made up of six rectangular metal walls which bound the vacuum chamber 2 (FIG. 2) therewithin. Of the six walls, a front wall is provided with a loading door (not shown) which can be opened in order to give access to the chamber before a vacuum is established therein. Duct means 22 are provided, connected at one end with one of the walls of the structure 1, for evacuating the chamber therewithin in known manner. An upper wall 3 of the structure is formed with a large circular aperture 4, the central axis 5 of which passes perpendicularly through the center of the wall 1.

For sealing the aperture 4, the apparatus includes a circular cover plate 6 the weight of which is supported by a circular thrust race 7 (FIG. 2) extending around the edge of the aperture 4 between the upper face of the wall 3 and the lower face of a flange portion 8 of the cover plate 6. The flange portion 8 extends radially outwardly, beyond the edge of the aperture 4, at the top end of a spigot portion of the plate 6, the spigot portion extending freely downwardly into the aperture 4 to locate the plate 6 with respect to that aperture. The spigot portion of the plate 6 fits with small clearance within the aperture 4, and carries a flexible sealing ring 9 which bears slidingly against the lateral bounding surface of the aperture 4 so as to provide a gastight bridge between the plate 6 and the wall 3.

The cover plate 6 is itself formed with a circular aperture 10, the central axis 11 of which is parallel to the axis 5 and spaced therefrom by a distance d.

The aperture is sealed by means ofa circular cover plate 12. The weight of the cover plate 12 is taken by a thrust race 13 extending around the edge of the aperture 10 and located between the cover plate 6 and a flange portion 143 of the cover plate 12.

The flange portion 14 extends radially outwardly, beyond the edge of the aperture 10, at the top end ofa spigot portion of the plate 12, the latter portion extending downwardly into the aperture 10 to locate the plate 12 with respect to that aperture. The spigot portion of the plate 12 carries a flexible sealing ring 15, which bears against the lateral boundary of the aperture 10 so as to form a gastight bridge between the plate 12 and the plate 6.

The cover plate 12 is formed with a small circular aperture 16, the central axis 17 of which is spaced from, but parallel to, the axis 1 l. v

The plate 12 is provided, around the aperture 16, with a circular bearing and vacuum-sealing device 18, incorporating flexible sealing rings 19 and 20 of known type, for receiving in vacuumtight manner the outlet end of an electron gun 21 (FIG. 2 only), allowing that end some rotational freedom (about the axis 17) with respect to the plate 12. The electron gun may be supported and movable in known manner by gantry means (not shown) above the wall 3. Thus the electron gun can be positioned to project a beam of electrons into the chamber 2 along the axis 17 ofthe aperture 16.

It will be appreciated that if the distance d between the axes l1 and 17 is equal to the distance d between the axes 5 and 11, the distance of the axis 17 from the axis 5 can be varied, by rotation of the plate 12 relatively to the plate 6, from zero to a maximum value 2d (corresponding to the cover-plate dispositions shown in the drawing). For a given positioning of the plate 12 relative to the plate 6, rotation of the plate 6 relative to the wall 3 then causes the electron beam (travelling along the axis 17) to sweep around the chamber in a circle. Thus, by appropriate rotation of the two plates 12 and 6, the electron beam can be taken to any position within a distance 2d of the central axis 5 of the chamber. The gun can be moved by its gantry means, and the cover plates 6 and 12 allowed to rotate to follow the imposed movement whilst maintaining vacuumtight sealing of the chamber 2, or alternatively the movement of the gun may be controlled by direct drives to the rotatable plates 6 and 12.

The slidable sealing rings 9 and 15 of course allow complete rotation of the plates 6 and 12 about their respective axes.

As an alternative, an enclosure unit embodying the present invention can be used to contain the workpiece in an argon arc welding process, for example, the workpiece being then surrounded by inert gas (for example at ambient atmospheric pressure) supplied into the working chamber. In such a case the said tool would of course be constituted by the movable welding electrode. In yet another application of the invention the said tool might be a laser.

1 claim:

1. An electron-beam working unit, comprising:

i. wall means having a. interior surfaces defining a chamber for accommodating a workpiece, and

b. edge regions defining a first aperture in the wall means;

ii. duct means having one end connected with the wall means for evacuating the said chamber therewithin;

iii. a first cover, for the first aperture a. having peripheral regions extending along the said edge regions,

b. rotatable with respect to the wall means about a first axis passing centrally and perpendicularly through the said first aperture, and

c. having inner edge regions which define a second aperture located eccentrically with respect to the said first aperture;

iv. a second cover, for the second aperture a. having peripheral regions extending along the inner edge regions of the first cover,

b. rotatable with respect to the first cover about a second axis passing centrally and perpendicularly through the second aperture, and

c. having inner edge regions defining a third aperture which is located eccentrically with respect to the second aperture;

first seal means extending completely around the said first aperture between the said wall means and the first cover to maintain a substantially vacuumtight seal therebetween during rotation of the first cover;

vi. second seal means extending completely around the said second aperture between the first and second covers to maintain a substantially vacuumtight seal therebetween during rotation of the second cover;

vii. an electron gun mounted externally of the said chamber and having an outlet located in register with the said third aperture for directing an electron beam into the chamber for operating upon such workpiece therein; and

viii. a sealing device mounted on the second cover and extending completely around the third aperture and cooperating with the electron gun to form a substantially vacuumtight seal over the third aperture;

whereby the point of incidence of the electron beam upon such workpiece stationary in the chamber when the unit is in use can be moved over the workpiece by combined rotation of the first and second covers.

2. A unit according to claim 1, wherein the said first axis and a third axis, which passes centrally and perpendicularly through the third aperture, parallel to the first and second axes, are equidistant from the said second axis.

3. A unit according to claim 1, wherein the said first aperture is circular and the said peripheral regions of the first cover define a circular edge thereof that fits freely within the said edge regions defining the first aperture.

4. A unit according to claim 3, wherein the said first seal means are located within the first aperture for providing a substantially vacuumtight seal between the said circular edge and the said edge regions defining the first aperture.

5. A unit according to claim 3, wherein the said first cover has a spigot portion, bounded laterally by the said circular edge, for locating the first cover with respect to the first aperture, and has a flange portion located at one end of the spigot portion and projecting radially outwardly beyond the said edge regions defining the first aperture.

6. A unit according to claim 5, further comprising a thrust race surrounding the first aperture and mounted between the said flange portion and the said wall means to reduce friction therebetween during rotation of the first cover plate with respect to the wall means.

7. A unit according to claim 1, wherein the said second aperture is circular and the said peripheral regions of the second cover define a circular edge thereof that fits freely within the said inner edge regions defining the second aperture.

8. A unit according to claim 7, wherein the said second seal means are located within the second aperture for providing a substantially vacuumtight seal between the said circular edge of the second cover and the said inner edge regions defining the second aperture.

9. A unit according to claim 7, wherein the second cover has a spigot portion, bounded laterally by the circular edge of the second cover, for locating the second cover with respect to the second aperture, and has a flange portion located at one end of its spigot portion and projecting radially outwardly beyond the said inner edge regions defining the second aperture.

10. A unit according to claim 9, further comprising a thrust race surrounding the second aperture and mounted between the first cover and the flange portion of the second cover for facilitating rotation of the second cover with respect to the first cover.

11. A unit according to claim 1, wherein the said sealing device includes means providing a slidable seal permitting the electron gun to be rotated with respect to the second cover about an axis passing perpendicularly through the third aperture.

+22% UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION atent.No- 3, 588,442 Dated June 28, 1971 Inventor(s) Kenneth Walter O'Riley It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r- Column 1, about line 15, change "10 to --lO to correspond to page 2 of the specification, line 13.

Signed and sealed this 29th day of February 1972.

(SEAL) Attest:

EDWARD M.FLETCHER ,JR. Attesting Officer ROBERI GOTTSCHALK Commissioner of Patents 

